body {
    font-family: Arial;
    background-color: skyblue;
    overscroll-behavior: none; /*阻止苹果设备因为触摸滑动时整个页面会拖动*/
}
#content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
}
button {
    cursor: pointer;
    border: none;
    padding: 2px 10px 2px 10px;
    height: 22px;
    border-radius: 5px;
    background-color: navy;
    color:white;
}
button:hover {
    background-color: mediumblue;
}
button:disabled,
button:disabled:hover {
    background-color: gray;
    cursor:default;
}